Silver halide color photography depends on the formation of dyes in order to reproduce an image. These dyes are typically formed from couplers present in or adjacent to the light sensitive silver halide emulsion layers that react to image light upon exposure. During development, the latent image recorded by the silver halide emulsion is developed by a developer compound to amplify the image. During this process, in which silver halide is reduced to elemental silver, the developer compound is at the same time oxidized to a species which then reacts or couples with the coupler compound present in or adjacent to the emulsion layer to form a dye of the desired color.
Typically, a silver halide emulsion layer containing a cyan dye-forming coupler is sensitized to red light. This facilitates so-called negative-positive processing, in which the image is initially captured in a negative format where black is captured as white, white as black, and the colors as their respective complementary colors, e.g., green as magenta, blue as yellow, and red as cyan. Then the initial image can be optically printed in the correct colors on a reflective background through the device of optical printing, which has the effect of producing a negative of the negative or a positive of the image.
Reversal color photographic elements and processes are well known in the art. They are described, for example, in T. H. James, editor, "The Theory of the Photographic Process". Reversal color photographic materials processed by such reversal color processes are generally classified into two types, one in which silver halide emulsion layers contains couplers, the other in which the silver halide emulsion layers do not contain couplers.
A reversal color photographic process fundamentally comprises a first development step with a black and white developer, a second development step with a color developer, and a desilvering step. More specifically, when an exposed reversal color photographic material is developed in the first development step, the exposed portions of the material are blackened as a result of development, but the unexposed portions remain unchanged. In the second development step, the silver halide in the unexposed portions is color developed to form colored dye and black silver images. In the exposed portions of the material, where little or no silver halide remains after the first development, little or no color image is formed by the color developer. The color photographic material thus developed is then processed in a desilvering step, where developed silver (Ag.sup.o) is oxidized by an oxidizing agent (bleach), and the oxidized silver is dissolved and removed from the color photographic material by a fixing agent or a silver halide complexing solvent. Thus, positive dye images are formed in the color photographic material. The desilvering step usually comprises a bleach step and a fix step or comprises a blix step (or bleach stabilization step) wherein bleaching and fixing (stabilization) are performed simultaneously.
It is important for a color coupler to show good dye-forming activity and also produce a desirable dye hue. In other words, a coupler must be capable of forming sufficient amount of dye density during the allowable development time of the process, and the dye formed by the reaction between the oxidized color developer must exhibit an absorption curve having a desirable wavelength, maximum absorption and shape so as to provide an accurate color rendition. Couplers that form cyan dyes upon reaction with oxidized color developer are described in such representative patents and publications as U.S. Pat. Nos. 3,041,236, 4,333,999; 4,883,746 and "Farbkupplereine Literature Ubersicht" in Agfa Mitteilungen, Band III, pp. 156-175 (1961). One type of commonly used cyan dye-forming coupler includes phenol compounds having carbonamido substituent groups in the 2- and 5-positions of the phenolic aromatic nucleus. Examples of such couplers are disclosed in U.S. Pat. Nos.4,333,999 and 4,923,791. While such couplers have been considered useful in photographic layers, they typically exhibit relatively low activity and produce dyes with less than optimal absorption curves.
The problem to be solved is to provide a silver halide photographic element containing a cyan coupler that exhibits high coupling activity and forms a dye having desirable light absorption characteristics and excellent image stability, particularly under conditions of elevated heat and humidity.